Until proper documentation will be released, figured you guys could use some of the info provided by devs. Trying to build this here and keep it clean.

- 3DS MAX OK? Version number? Special scripts, settings, export or nKP ASE-style and AC-own editor?!
FBX 2012, any cad that export that format is ok.
- Polygon numbers/style?
There's only memory limit, enough to make a track. The style of polygons?? we're talking about triangles (and to be more precise of vertices) so the style should be... a triangle, possibly well shaped (you can work with polys but It would be better to triangulate by the exporter when exporting). The only limit is the number of coordinates that a mesh can have, 65536. Coordinates are vertices, normals, UVs and more. There's no way to check this before exporting, but the editor will warn you, when importing, if an object exceeds that number (the object will not be imported), giving you the possibility to divide it into more objects. (back in the cad)
- Measure Units (metric, Generic, inch, millimeter, meter)!?
We use meters.
- Standard Object Names (AC_Start, AC_Finish, AC_Time, AC_Pit, AC_Road ect.)?!
It's early... start your project first. (how do you know about AC_START or AC_PIT?)

no rules on texture names, size is limited by your graphic card (usually 8192x8192, even if I strongly suggest NOT to use such a big one). textures can be only PNG or DDS (I STRONGLY suggest to use dds). Any kind of dds format is supported except compressed normal maps, palette and signed ones

Instances are not supported. if Transparent means opacity then we support alpha test and alpha blend opacity. Transparent for us is an object that is rendered last in the drawing order (used for some Alpha Blended objects).
An object can be flagged (in our editor) not to cast the shadow. To make an object not receiver you'll have only one or 2 shaders that do that.
Collision: Any object with a number in front of it becames physic, and the number identifies the sector number (exactly as like as in nKpro). If you call an object 01MUD then you'll have to define that name on surfaces.ini of the track. the only exception is WALL (01WALL, 02WALL ecc ecc)that is by default the mesh collider and can't be modified. There are some default definitions that could help, like ROAD, GRASS, SAND, KERB
Any track must be divided into several sectors, depending on the complexity of the physical meshes.
In this case you could study the workflow of nKpro, it's quite similar.

Please give any info, description for possible to work now.
One track making is 6-9 months.
If Assetto Corsa v1.0 (+DevKit, info, help) 2014 half, the first modding track 2015...​

I'll explain only 2 things that maybe could help:
1) If you're already placing trees (even if I think it's still not the time for trees if you've just started your project:
In your Cad place trees as single objects (don't join them). Place the pivot point at the center of the tree.
Call the tree KSTREE_GROUP_"any name"_1 (2,3,4,5,6 ecc).
They'll be joined in one object once imported called "any name". This let you the freedom to add or cut trees from the scene in the cad much easier
2) WE DON'T SUPPORT DOUBLE FACE MESHES, so if you want to see the back of a face you'll have to model it and give volume to objects, to avoid shadow problems.

Pits position must be named:
AC_PIT_n (n must be 1, 2, 3, 4 etc) DON'T name it AC_PIT_01 (01 is different from 1)

Start positions must be named:
AC_START_n

Hotlap start position must be named:
AC_HOTLAP_START_0

In general anything related to a position must follow this rule: the Y axis of the pivot point must point UP and the Z axis must point forward and will determinate the orientation of the car. This is VERY important for 3dStudioMax users, where usually Z axis is UP and Y axis is Forward, beware.

Timing:
These objects don't need the axis orientation like the spawn objects
AC_TIME_0_L
This must be placed on the LEFT side of the start/finish
AC_TIME_0_R
This must be placed on the RIGHT side of the start/finish

AC_TIME_1_L
AC_TIME_1_R
Same rule about left and right but it will became the first intermediate.
AC_TIME_2_L
AC_TIME_2_R
The second intermediate.
You can place only 2 intermediates.

The trigger will be a line drawn from the center of the object to the other side (not visible obviously)

Audio generator
AC_AUDIO_anyname
This works in conjuntion with audiosources.ini in data folder. For any object you must specify a wave to be played. It works like a speaker so the sound will always have a direction (not suitable for ambient sounds). I suggest not to exagerate with the number of AC_AUDIO in your scene.

Names used for A to B point are not completely functional and unsupported.
AC_OPEN_START_L
AC_OPEN_START_R

AC_OPEN_FINISH_L
AC_OPEN_FINISH_R

I suggest to use a cube for any of these objects, mapped with a material (no need to use a unique material, just use any material you've already used in the scene)

Just draw a cube and rotate ONLY THE PIVOT on the X axis, that's it: you got the Y axis pointing up and the Z pointing forward. Then you have to rotate THE ENTIRE OBJECT to give a direction for the car. (the problem comes from some cad that uses Z axis for UP and x,y for dimensions, it's a problem that comes from the old 2d Cads where you have X and Y. But a graphic card "thinks" different. Z is the depth, is the forward.

After changing the pivot, don't do anything, (refering to 3dstudio max, reset Xform for example)

I'll update the example soon, with a better placement of the spawn points. It happened also to us: car perfectly positioned for me and others, and car flying away for one. Changed the position a bit and perfect for everybody.
Don't put the box too low, it can stay at 1 or more meters from the ground, the car will be placed on the surface, not on the spawn and let fall down

You don't need surfaces.ini. You need it if you are going to make a new kind of surface, but there are presets such as ROAD, SAND, GRASS, KERB, WALL.
Those are pre defined surfaces and don't need to be defined.

You need to name the road, where you spawn "01ROAD01", I don't know how AC works for the road, but i divided the road in many parts.

I don't think there's a default pit road, so you can put a new surface in the *.ini and turn to 1 the parameter IS_PITLANE

Have you tried moving the spawn point to where you want, then going into hierarchy, then affect pivot only and then Alignment, center to object ? Looks like it's not moving the pivot point of the spawn object when you move it.

1/ The more different shaders you have on your track, the more the performance will be affected. I am not sure there is a maximum number (staying in the reasonable limits) but I think I remember Si3v saying we shouldn't need to go above 50 for a track (that's estimate budget in official tracks).

2/ Virtually, there's no limit (as in a fixed number); devs said the only limitation is your memory.
However, do note:
- from other user experience when going above 2.5 - 3 millions verts you might experience some editor issues (crashes). And even this, might not be a limitation anymore, since the use of layouts (they've used this to split the Nords in many smaller meshes and workaround the limitations) - I haven't test it yet, didn't do a track that big .
- one single mesh/object can't have more that 65k verts. LE: coordinates, not verts. 65536 to be precise. Coordinates are vertices, normals, UVs and more. If needed, you'll have to split it.
- for information, a track like Imola, has around 3 millions verts (from which about 1.5 are for vegetation).

So what I'm basically saying, unless you are doing a hugely detailed project, you probably don't need to worry about verts limit.

Also, from what I experience testing, the more 1WALL you have, the less FPS you'll get. I have created some special collidable trees / vegetation & the FPS has dropped to 50%, so it's not a good idea to create too many physical objects in your scene.